Resolve modern meta-schemas also with an empty fragment (#1816)

Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>

Author: jviotti

src/core/jsonschema/official_resolver.in.cc

@@ -52,6 +52,11 @@ auto sourcemeta::core::schema_official_resolver(std::string_view identifier)
     return sourcemeta::core::parse_json(
         R"EOF(@METASCHEMA_JSONSCHEMA_2020_12_OUTPUT@)EOF");
 
+    // Just for compatibility given that this is such a common issue
+  } else if (identifier == "https://json-schema.org/draft/2020-12/schema#") {
+    return sourcemeta::core::parse_json(
+        R"EOF(@METASCHEMA_JSONSCHEMA_2020_12@)EOF");
+
     // JSON Schema 2019-09
   } else if (identifier == "https://json-schema.org/draft/2019-09/schema") {
     return sourcemeta::core::parse_json(
@@ -98,6 +103,11 @@ auto sourcemeta::core::schema_official_resolver(std::string_view identifier)
     return sourcemeta::core::parse_json(
         R"EOF(@METASCHEMA_HYPERSCHEMA_2019_09_OUTPUT@)EOF");
 
+    // Just for compatibility given that this is such a common issue
+  } else if (identifier == "https://json-schema.org/draft/2019-09/schema#") {
+    return sourcemeta::core::parse_json(
+        R"EOF(@METASCHEMA_JSONSCHEMA_2019_09@)EOF");
+
     // JSON Schema Draft7
   } else if (identifier == "http://json-schema.org/draft-07/schema#" ||
              identifier == "http://json-schema.org/draft-07/schema") {

test/jsonschema/jsonschema_official_resolver_test.cc

@@ -31,6 +31,9 @@ TEST(JSONSchema_official_resolver, jsonschema_2020_12) {
   EXPECT_SCHEMA("https://json-schema.org/draft/2020-12/meta/validation");
   EXPECT_SCHEMA("https://json-schema.org/draft/2020-12/links");
   EXPECT_SCHEMA("https://json-schema.org/draft/2020-12/output/schema");
+
+  // Just because a lot of people get this wrong
+  EXPECT_SCHEMA("https://json-schema.org/draft/2020-12/schema#");
 }
 
 TEST(JSONSchema_official_resolver, jsonschema_2019_09) {
@@ -45,6 +48,9 @@ TEST(JSONSchema_official_resolver, jsonschema_2019_09) {
   EXPECT_SCHEMA("https://json-schema.org/draft/2019-09/output/schema");
   EXPECT_SCHEMA("https://json-schema.org/draft/2019-09/links");
   EXPECT_SCHEMA("https://json-schema.org/draft/2019-09/output/hyper-schema");
+
+  // Just because a lot of people get this wrong
+  EXPECT_SCHEMA("https://json-schema.org/draft/2019-09/schema#");
 }
 
 TEST(JSONSchema_official_resolver, jsonschema_draft7) {